Charge preamplifier

Abstract

A charge preamplifier for converting an electric charge generated in a charge source sensor into a voltage signal, including: a phase inverting amplifier including an input related to the charge source sensor, and an output for providing the voltage signal; a storage capacitor connected between the input and the output of the phase inverting amplifier; a reset system connected to the input of the phase inverting amplifier, for providing to the storage capacitor a discharging current as a function of a control signal, and a control element including: a first input connected to the output of the phase inverting amplifier, for withdrawing the voltage signal, a second input subjected to a reference voltage, a set of components configured and arranged to generate a control signal proportional to the deviation between the voltage signal and the reference voltage, the proportionality coefficient being lower than one in a high frequency band, an output connected to the reset system to provide thereto the control signal.

The invention claimed is: 
     
       1. A charge preamplifier for converting an electric charge generated in a charge source sensor into a voltage signal, comprising:
 a phase inverting amplifier including an input related to the charge source sensor, and an output for providing the voltage signal; 
 a storage capacitor connected between the input and the output of the phase inverting amplifier; 
 a reset system connected to the input of the phase inverting amplifier, for providing to the storage capacitor a discharging current as a function of a control signal, and 
 a control element including:
 a first input connected to the output of the phase inverting amplifier, for withdrawing the voltage signal, 
 a second input subjected to a reference voltage, 
 a set of components configured and arranged to generate a control signal proportional to the deviation between the voltage signal and the reference voltage, said proportionality coefficient being lower than one in a high frequency band, and 
 an output connected to the reset system to provide thereto the control signal, 
 
 wherein the control element includes a modified transconductance amplifier including
 a resistive element, 
 a first field effect transistor of a first type, the gate and the drain of the first transistor being connected with each other, 
 a second field effect transistor of the same type as the first transistor the sources of the first transistor and the second transistor being at a same fixed potential, the gates of the first transistor and the second transistor being connected via the resistive element, and 
 a capacitor connected between the gate and the drain of the second transistor. 
 
 
     
     
       2. The charge preamplifier according to  claim 1 , wherein said proportional coefficient is higher than one for low frequencies. 
     
     
       3. The charge preamplifier according to  claim 1 , wherein the resistive element includes a second transconductance amplifier, biased by a low current. 
     
     
       4. The charge preamplifier according to  claim 1 , wherein the control element includes:
 a D.C. current source, 
 a third field effect transistor of a complementary type to the first transistor, such that:
 the drain of the third transistor is connected to the drain of the first transistor, 
 the source of the third transistor is connected to the current source, 
 the gate of the third transistor is subjected to the output voltage of the phase inverting amplifier, 
 
 a fourth field effect transistor of a complementary type to the first transistor, such that:
 the drain of the fourth transistor is connected to the drain of the second transistor, 
 the source of the third transistor is connected to the current source, 
 the gate of the third transistor is subjected to the reference voltage. 
 
 
     
     
       5. A charge preamplifier for converting an electric charge generated in a charge source sensor into a voltage signal, comprising:
 a phase inverting amplifier including an input related to the charge source sensor, and an output for providing the voltage signal; 
 a storage capacitor connected between the input and the output of the phase inverting amplifier; 
 a reset system connected to the input of the phase inverting amplifier, for providing to the storage capacitor a discharging current as a function of a control signal, and 
 a control element including:
 a first input connected to the output of the phase inverting amplifier, for withdrawing the voltage signal, 
 a second input subjected to a reference voltage, 
 a set of components configured and arranged to generate a control signal proportional to the deviation between the voltage signal and the reference voltage, said proportionality coefficient being lower than one in a high frequency band, 
 an output connected to the reset system to provide thereto the control signal, 
 
 wherein the control element includes:
 an operational amplifier, including:
 a non-inverting terminal subjected to the voltage signal, 
 an inverting terminal subjected to the reference voltage, 
 an output connected to a passive network, 
 
 the passive network including:
 a first resistance, including a first terminal connected to the output of the operational amplifier, and a second terminal at which the voltage signal is withdrawn 
 a second resistance, including a fist terminal connected to the second terminal of the first resistance, and a second terminal 
 a third resistance including a first terminal connected to the second terminal of the second resistance and a second terminal subjected to a zero voltage 
 a second capacitor, connected in parallel with the second resistance. 
 
 
 
     
     
       6. The charge preamplifier according to  claim 1 , wherein the reset system includes a field effect transistor the source of which is subjected to the control signal. 
     
     
       7. The charge preamplifier according to  claim 1 , wherein the reset system includes a bipolar transistor the emitter of which is subjected to the control signal. 
     
     
       8. The charge preamplifier according to  claim 1 , wherein the reset system is biased by a leakage current of the sensor.